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Abstract
A bandwidth-tunable balanced filter (BTBF) is proposed, which utilizes the quarter-wavelength coupled lines with multi-point loaded varactors and half-wavelength transmission lines. The varactor-loaded coupled lines combined with the pair of the half-wavelength transmission lines provide the basic wideband differential-mode (DM) passband and common-mode (CM) suppression, and the loaded varactors can tune the lower edge, the upper edge and the impedance matching (IM) of the passband. Thus, tunable bandwidth with almost constant center frequency can be achieved by controlling the bridged varactor Cv1 and the series varactors Cv2 and Cv3. Compared to the state-of-the-art designs, the proposed design offers significant advantages of broad tuning range of DM bandwidth, wide minimum DM bandwidth, low insertion loss, and simple structure. For demonstration, a prototype is designed with the DM bandwidth tuning range of 24.7%, the minimum DM fractional bandwidth (FBW) of 46.5%, the maximum insertion loss inside the IM bandwidth of 2.3 dB.
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Notes on contributors
Xianlong Dou
Xianlong Dou was born in Xuzhou, Jiangsu Province, China, in 2000. He received the B.S. degree in electronic science and technology in 2022 from Nantong University, Nantong, China, where he is currently working toward the M.S. degree in Information and Communication Engineering. His current research interests include RF/microwave components, differential microwave circuits, and tunable circuits.
Wei Zhang
Wei Zhang was born in Suqian, Jiangsu Province, China, in 1985. She received the B.S. and M.S. degrees in 2004 and 2008, respectively, from Nantong University, Nantong, China, where she is currently working toward the Ph.D. degree in electromagnetic field and microwave technology. Since 2011, she has been with Xinglin College, Nantong University, where she is currently a Lecturer. Her current research interests include RF/microwave components and differential circuits.
Jianpeng Ren
Jianpeng Ren was born in Datong, Shanxi Province, China, in 1998. He received the B.S. degree in electronic information engineering in 2021 from Tianjin Urban Construction University, Tianjin, China. He received the M.S. degree in Information and Communication Engineering in 2024 from Nantong University, Nantong, China. His current research interests include RF/microwave components, differential microwave circuits, and tunable circuits.
Jin Shi
Jin Shi (Member, IEEE) received the B.S. degree in physics education from HuaiYin Teachers College, Huai'an City, China, in 2001, the M.S. degree in radio physics from the University of Electronic Science and Technology of China, Chengdu, China, in 2004, and the Ph.D. degree in electronic engineering from the City University of Hong Kong, Hong Kong, in 2011. From 2004 to 2006, he was a Research Engineer in Comba, where he was involved with the RF repeater system. From 2007 to 2008, he was a Research Assistant with the City University of Hong Kong. He was a Research Fellow Institute for Infocomm Research, Singapore, where he was a Scientist from 2011 to 2013. In 2013, he joined the School of Electronics and Information, Nantong University, China, as a Professor. From 2019, he was also a Group Leader of Research Center for Intelligent Information Technology. His current research interests include RF/microwave components and subsystems, antennas, differential circuit, and dielectric circuits and antennas.